Most of Trump’s charts skew the data. And not always in his favor.

Donald Trump’s campaign is obsessed with favorable poll results, as evidenced by a graphic deluge on official social media channels. It’s a marked difference from their Democratic rival who has led polling averages throughout most of the campaign. And while neither candidate has
a perfect record when it comes to
spinning the data, only the Trump campaign has used a combination of cherry-picked polls and misleading data visualization to paint a cheerier picture of its prospects on Election Day.

How tall are the bars in the chart? Instead of ending at a clearly defined baseline, the bars fade to black. But if we add a baseline at the bottom of the graphic, the implied scale doesn’t match the numbers.

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Implied baseline

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Implied baseline

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Implied baseline

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The chart visually inflates Trump’s two-point lead to over 11 points. If we adjust our scale to match the data, where would the baseline end up? In other words, how tall should the bars actually be?

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The real baseline is

way down there

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The real baseline is

way down there

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The real baseline is

way down there

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Keep scrolling!

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Almost there!

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Data visualization can help people understand information by representing data with graphical properties, such as size, shape or color. Bar charts represent data using length. This means that if the bars don’t begin at zero, comparisons between bar lengths will distort the data — and a reader’s comprehension of the numbers. In the extreme example below, bars A and B are nearly equal in length but we can exaggerate A’s lead over B by cutting off the scale. The distortion can also work in reverse.

EXAGGERATING A LEAD

A

B

A

B

Baseline

DIMINISHING A LEAD

A

A

B

B

EXAGGERATING A LEAD

DIMINISHING A LEAD

A

B

A

A

A

B

B

B

Baseline

EXAGGERATING A LEAD

DIMINISHING A LEAD

A

B

A

A

A

B

B

B

Baseline

Trump’s charts often distort comparisons by hiding or misplacing the baseline, mostly exaggerating his lead, but sometimes diminishing it. Here’s what happens when we put all of Trump’s charts on the same scale:

Accurate

The chart

above

These charts diminish Trump’s lead.

Close enough.

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These charts exaggerate the appearance of Trump’s lead.

Edge of graphic nearly meets baseline

Baseline meets clearly-defined bar.

SCROLL

YOU MADE IT.

KEEP SCROLLING!

NEARLY THERE!

The chart

above

Same graphic,

different scales

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20

10

0

These charts exaggerate the

appearance of Trump’s lead.

Same graphic,

different scales

Close enough.

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40

30

20

10

0

Edge of graphic nearly meets baseline.

Same poll,

different scales

Accurate

50

40

30

20

10

0

These charts diminish Trump’s lead.

Baseline meets clearly-defined bar.

The chart

above

Same graphic,

different scales

50

40

30

20

10

0

These charts exaggerate the

appearance of Trump’s lead.

Same graphic,

different scales

Close enough.

50

40

30

20

10

0

Edge of graphic nearly meets baseline.

Same poll,

different scales

Accurate

50

40

30

20

10

0

These charts diminish Trump’s lead.

Baseline meets clearly-defined bar.

The chart

above

Same graphic,

different scales

50

40

30

20

10

0

These charts exaggerate the

appearance of Trump’s lead.

Same graphic,

different scales

Close enough.

50

40

30

20

10

0

Edge of graphic nearly meets baseline.

Same poll,

different scales

Accurate

50

40

30

20

10

0

These charts diminish Trump’s lead.

Baseline meets clearly-defined bar.

Some of Trump’s charts fade to black or otherwise obscure the baseline, while others imply a baseline that doesn’t match the data the charts purport to display.

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Baseline obscured,

bars fade

False baseline

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Baseline obscured,

bars fade

False baseline

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Baseline obscured,

bars fade

False baseline

The implied scales on Trump’s charts vary wildly even within the same graphic. The distortion is not always beneficial to Trump — some charts make Trump’s lead over Clinton appear smaller rather than larger.

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One chart, from
a July 18 tweet showing a Trump lead among members of the military, accurately displayed the data. The graphic doesn’t name a source, but the data appears to come from
a Military Times poll of “active-duty troops, reservists and National Guard personnel,” including third-party and write-in candidates.

What about Hillary Clinton?

The Clinton campaign posts charts sparingly compared with the Trump. They use data visualization to illustrate campaign issues and policy, rather than poll numbers. For example, here’s a bar chart from the campaign’s Instagram account, posted
in April.

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Clinton’s bar chart, which compares wage gaps between men and women by race, also has scale issues. The chart uses light gray bars to represent 100 percent of the median wage of white men. The bar comparing the median wage of Asian-American women to that of white men is labeled 84 percent but reaches nearly 90 percent. This scale error makes the wage gap appear smaller than the data suggests it really is.

The bottom line

Bar charts should always have a clear baseline, representing zero on the scale. Bar charts must begin at zero to avoid distorting length comparisons. Whether you are viewing or creating a data visualization, check that the chosen scale does not distort the data. For bar charts, a zero baseline is the difference between data visualization and data spin.

All of Trump’s charts

Date posted

Trump margin

Pollster

July 18

+29

Military Times

Military

July 25

+3

PPP

Ohio

July 25

+11

CNN/ORC

Other

July 25

+5

CNN/ORC

National

July 25

+4

LA Times/USC

National

July 25

+4

Morning Consult

National

July 26

+9.4

InsideSources/NH Journal

N.H.

July 26

+5

Rasmussen Reports/KTNV-TV

Nev.

July 26

+9.4

InsideSources/NH Journal

N.H.

July 27

+7

LA Times/USC

National

Aug. 1

+24

RABA Research

Okla.

Aug. 1

+4

RABA Research

Va.

Aug. 24

+2

Florida Atlantic University

Fla.

Aug. 26

+3

Florida Chamber of Commerce

Fla.

Aug. 26

+1

LA Times/USC

National

Aug. 26

+1

UPI/CVoter

National

Sept. 2

+3

LA Times/USC

National

Sept. 8

+22

NBC*

Other

Sept. 12

+5

Bloomberg

Ohio

Sept. 14

+4

JMC Analytics

Fla.

Sept. 14

+4

Quinnipiac

Ohio

Sept. 14

+4

Quinnipiac

Ohio

Sept. 14

+3

Suffolk

N.C.

Sept. 16

+4

Emerson

Colo.

Sept. 16

+4

CNN/ORC

Fla.

Sept. 17

+2

Monmouth

Nev.

Sept. 18

+2

Emerson

National

Sept. 19

+7

LA Times/USC

National

Sept. 21

+3

Suffolk

Ohio

Sept. 22

+5

Rasmussen Reports

National

Sept. 22

+5

FOX News

Ohio

Sept. 22

+13

FOX News

Nev.

Oct. 5

+2

Reuters/Ipsos

Ariz.

Oct. 5

+2

Reuters/Ipsos

Colo.

Oct. 5

+7

Reuters/Ipsos

Iowa

Oct. 5

+13

Reuters/Ipsos

Ga.

Oct. 5

+5

Reuters/Ipsos

S.C.

Oct. 18

+2

LA Times/USC

National

Oct. 31

+4

Remington Research

Fla.

Oct. 31

+4

LA Times/USC

National

*This appears to be the partial results of a non-scientific Twitter poll. The Trump campaign did not respond to a request for clarification about the source of this poll.

Source: Donald Trump and Hillary Clinton campaign social media. Originally published Oct. 21.